Heat recovery units are used in, amongst others, ventilation systems for e.g. ventilating buildings and at the same time returning the heat out of the exhaust air which is ventilated out from the building to the exterior air which is fed into the building in the form of inlet air.
A heat recovery assembly which is present on the market, has two plate housings which each surround their own regenerative plate package which forms the heat accumulators. Each plate housing is mutually joined with two valve housings. Each valve housing comprises a valve leaf which are each influenced by their own valve motor. One of the valve housings is equipped with a supply air fan which is connected to a supply air channel on the valve housing, and with an exhaust air fan which is connected to an exhaust channel on the valve housing. The valve housing itself is connected to each and all of the plate housings via a supply air opening resp. an exhaust air opening on the respective plate housings. The second valve housing is equipped with a used-air channel and an exterior air channel and is connected to each of the plate housings via a used-air opening resp. an exterior air opening of the respective plate housings.
Exhaust air resp. exterior air passes alternately through the plate packages. When one of the plate packages has warmed up and the other has cooled, the valve leaves in the valve housings are switched over, whereby the exhaust resp. exterior air changes plate package and have the opposite direction of flow compared with the air which previously flowed in the respective plate packages.
Another existing heat recovery assembly is the rotation heat exchanger where a continuous airflow flows through a rotating cylinder. The axis of rotation of the cylinder extends into a plane which coincides with a wall. On one side of the wall, warm air flows and on the other side cold air flows. By letting the warm air pass through the cylinder, the part of the cylinder which is on the "warm" side is warmed up. When the cylinder rotates, the warmed up part of the cylinder will go over to the "cold" side, whereby the cold air which flows through the cylinder is warmed up.